This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2001-081123, filed Mar. 21, 2001, the entire contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to an ink jet printer, and in particular, to an ink jet printer comprising an ink head which can prevent a recording medium from being contaminated by waste ink after a purging operation.
2. Description of the Related Art
Various kinds of image recording apparatuses are known. In recent years, ink jet printers adopting an inkjet recording system are widely used for the reason that they are relatively low-priced and small-sized. The ink jet printer has an ink head, a moving mechanism and a conveying mechanism. The ink head jets ink to a recording medium. The moving mechanism moves the ink head relative to the recording medium. The conveying mechanism moves the recording medium relative to the ink head.
The ink jet printer intermittently conveys the recording medium by the driving of the conveying mechanism. During the conveying operation, a separated distance between the recording medium and a surface of the ink head opposing to the recording medium, that is, a front surface of the ink head is about several millimeters.
The ink jet printer drives the ink head and jets ink, while the recording medium stops during the intermittent conveying operation. In this way, the ink jet printer forms a desired image on the recording medium.
The ink jet printer further has a platen. The platen holds the recording medium by a negative pressure. In this way, the recording medium is prevented from approaching to the side of the front surface of the ink head. That is, the platen operates so as to keep a constant space between the front surface of the ink head and the recording medium.
The ink head has an ink chamber and a nozzle. The ink chamber is a portion to store ink before ejection. The nozzle is an ejection aperture to jet the ink. In general, the ink head fails a print when bubbles enter the ink chamber or the nozzle is clogged with paper dust.
Accordingly, the ink jet printer periodically performs a maintenance process for preventing the print failure. For this reason, the ink jet printer has a maintenance mechanism for performing the maintenance process. In general, the maintenance mechanism has a cap, sucking means and a wiper blade. The cap is formed so as to be able to cover at least one nozzle. The sucking means is connected to the cap. The sucking means applies a negative pressure to the inside of the cap. The wiper blade is configured so as to be able to wipe out ink on a nozzle-forming surface (a front surface of the ink head).
This maintenance process is performed after the ink head is moved to a maintenance station. In this maintenance process, the maintenance mechanism performs a purging operation and a wiping operation. The purging operation is an operation to suck impurities (dust and bubbles) inside the nozzle and/or the ink Hi chamber together with the ink. The wiping operation is an operation to eliminate the ink remained on the nozzle-forming surface (the front surface of the ink head).
In the purging operation, first, the cap of the maintenance mechanism caps the nozzles of the ink head which is an object of the maintenance. Subsequently, the maintenance mechanism applies a negative pressure to the inside of the cap and sucks the ink inside the nozzle. After this purging operation, the large amount of ink (waste ink) remains on the nozzle-forming surface.
In the purging operation, the wiper blade wipes the large amount of waste ink remained on the nozzle-forming surface. In the specification, the ink remained on the front surface of the ink head is referred to as xe2x80x9cwaste inkxe2x80x9d.
By the maintenance process, each nozzle of the ink head keeps a state of being able to jet ink always normally.
However, even when the wiping operation is performed, it is difficult to completely wipe out the ink on the front surface of the ink head. The waste ink remained on the front surface of the ink head gradually flows downward. The waste ink collects in the lower side of the ink head front surface. The waste ink collected in this way swells from the front surface of the ink head. Accordingly, when the space between the recording medium and the front surface of the ink head is narrowed in this state, the waste ink is brought into contact with the recording medium. For example, the contact occurs when the recording medium is lifted from the platen at the time of the image forming.
Various ink heads are suggested to solve the problem. For example, the ink head disclosed in Jpn. Pat. Appln. KOKAI Publication No. 11-998 has the nozzle plate which curve to solve the problem. Concretely, the ink head has the front and rear surface. The nozzle plate is arranged in the front surface. As going downward, this nozzle plate curves toward the rear surface so that the space between the plate and the recording medium becomes larger. In other words, the ink head is formed so as to be in a tapered shape. With the ink head formed in this way, the waste ink which flows downward along the surface of the nozzle plate gradually separates from the recording medium. Therefore, this ink head reduces the possibility for the waste ink to remain on the recording medium. However, in the invention disclosed in this publication, the waste ink that descended toward the lowest end of the ink head gradually collects without place to go. For this reason, the collected waste ink finally drops by its own weight. When the waste ink drops, the waste ink contaminates the periphery of the ink head.
An ink head 1010 shown in FIG. 12A has ribs 1021 on its front surface. The ribs 1021 prevent the recording medium lifted from a platen from contacting a nozzle plate 1030 having a nozzle 1031. The ribs 1021 are formed in the periphery of the nozzle 1031 in front of the ink head 1010. The ribs 1021 project toward the side of the recording medium rather than the front surface of a nozzle plate 1030 (see FIG. 12B). Accordingly, the space between the distal end of the rib 1021 and the recording medium is smaller than the space between the front surface of the nozzle plate 1030 and the recording medium. Hence, the waste ink remained on the distal end of the rib 1021 is easily contacted by the recording medium.
Particularly, when an angular portion is formed along the longitudinal axis of the rib 1021 (see FIG. 12A), the waste ink 80 remains in a state of being swollen on the angular portion or slightly upward from the angular portion (see FIG. 12C). For this reason, there is strong possibility that, in the vicinity of the angular portion, the recording medium is brought into contact with the waste ink. When the rib 1021 is formed in the periphery of the nozzle in this way, the front surface of the ink head 1010 is not a uniform plane. Therefore, it is difficult for the wiper blade to effectively wipe out the waste ink on a nozzle plate 1030 in the wiping operation. Accordingly, the large amount of waste ink remains on the front surface of the nozzle plate 1030 even after the wiping operation.
The present invention is to solve the problems. An object of the present invention is to provide an ink jet printer that prevents contamination by waste ink or reduces contamination by waste ink to a lower degree.
In order to solve the problem and achieve the object, the ink jet printer according to the present invention is constituted as follows.
An ink jet printer according to a first aspect of the present invention comprises at least one ink head which jet ink to a recording medium surface of a recording medium. The ink head has a nozzle plate which has at least one nozzle for jetting ink, and at least one rib which projects toward the side of the recording medium rather than the nozzle. The rib is gradually tapered toward the side of the recording medium.
An ink jet printer according to a second aspect of the present invention comprises at least one ink head and at least one ink absorber. The ink head is opposed to a recording medium and jets ink to the recording medium. Further the ink head comprises a nozzle-forming surface and a curved surface. The nozzle-forming surface and the curved surface are opposed to the recording medium. The nozzle-forming surface has at least one nozzle for jetting ink. As going downward in a vertical direction, the curved surface curves so as to separate from the recording medium. The ink absorber is detachable from the curved surface.
An ink jet printer according to a third aspect of the present invention comprises at least one ink head, at least one slit, and an ink absorber. The ink head is opposed to a recording medium. The ink head jets ink to the recording medium. Further the ink head comprises a nozzle-forming surface and a curved surface. The nozzle-forming surface and the curved surface are opposed to the recording medium. The nozzle-forming surface has at least one nozzle for jetting ink. As going downward in a vertical direction, the curved surface curves so as to separate from the recording medium. The slit extends along the longitudinal axis of the ink head on the curved surface. Further, the slit reaches until a surface opposite to the surface of the ink head opposing to the recording medium. The ink absorber is provided in the region where the slit is formed in the surface opposite to the surface of the ink head opposing to the recording medium.
An ink jet printer according to a fourth aspect of the present invention comprises at least one ink head, and at least one ink absorber. The ink head is opposed to a recording medium and jets ink to the recording medium. Further the ink head comprises a nozzle-forming surface and a curved surface opposed to the recording medium. The nozzle-forming surface has at least one nozzle for jetting ink. As going downward in a vertical direction, the curved surface curves so as to separate from the recording medium. The ink absorber is fixed to at least a part of the curved surface.
An ink jet printer according to a fifth aspect of the present invention comprises at least one ink head, and at least one ink absorber. The ink head is opposed to a recording medium and jets ink to the recording medium. The ink head comprises a nozzle-forming surface and an angular portion. The nozzle-forming surface and the angular portion are opposed to the recording medium. The angular portion is formed by the nozzle-forming surface and a surface intersecting the nozzle-forming surface. The ink absorber is fixed to the ink head such that at least a part thereof contacts the angular portion.
An ink jet printer according to a sixth aspect of the present invention comprises at least one ink head and at least one ink absorber. The ink head is opposed to a recording medium and jets ink to the recording medium. The ink absorber is detachable from a surface of the ink head opposing to the recording medium. This ink absorber contacts the surface of the ink head opposing to the recording medium at the end of a purging operation of the ink head.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.